The present invention concerns an improvement for a hexapod.
A hexapod can, for example, be used as a sub-assembly of a tooling machine used for positioning a tool with respect to a part to be machined. Hexapods can also be used in other applications, for example, to perform physical measurements.
A hexapod includes two plates, a working plate and a base plate, which are interconnected by six legs. The legs are articulated and extensible for varying, at will, the relative position of the working plate with respect to that of the base plate. Positioning and movement of the legs of the hexapod are controlled by a computer. An example of a hexapod of this type is described in EP 0 489 857.
It has been found to be desirable to provide a device that can reduce or compensate for stresses on the assembly of elements comprising the hexapod, particularly the legs and articulating parts of the hexapod.
For example, a hexapod for positioning a tool with respect to a part to be machined includes two plates, a mobile plate and a base plate, which are interconnected by six articulated and extensible legs for varying, at will, the relative position of the mobile plate with respect to that of the base plate. In accordance with the present invention, the hexapod is provided with a device for reducing or compensating for stresses on at least one of the elements of the hexapod.
To this end, a jack is provided which is received by a fixed surface and which operates to support the weight placed on the mobile plate of the hexapod. The jack can be placed vertically, including a rod which is fixed to the periphery of the mobile plate. As an alternative, the jack can be non-vertically positioned, and the compensating forces can be transmitted by a return pulley to an attachment point on the mobile plate. As a further alternative, the jack can control a movable arm which is then connected to the mobile plate.
Stresses on elements of the hexapod can also be reduced or compensated for by controlling the logic (in software) which is used to define at least one force-limiting criterion for operation of the hexapod. It is also possible to combine a mechanical compensation device with control of the logic (in software) for defining force-limiting criteria for operating the hexapod.
The present invention is further described below, with reference to the following figures.